"I'm Still Here"

Joaquin Phoenix has been booked for David Letterman's "Late Show," and here's hoping it's as awkward and unintentionally hilarious as his last appearance.

Phoenix, 35, was last a guest with Letterman on Feb. 11, 2009, sporting a ZZ Top beard, refusing to engage in anything resembling a conversation and telling Letterman he planned to pursue a career as a rapper. Since then, debate about whether the "Walk the Line" star was putting everyone on or is now officially nuts has only been stoked by a new documentary.

Phoenix will appear on Letterman Sept. 22 to promote the new film, directed by his brother-in-law Casey Affleck and titled "I'm Still Here." The best way to generate hype for the film might be a redux of his last appearance, in which an exasperated Letterman ridiculed the Oscar winner, even asking him about life with Unabomber Ted Kaczynski and dismissing him with the words, "I'm sorry you couldn't be here tonight."

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The film, which purports to show Phoenix's attempt to become a hip hop artist, has generated wildly varying reviews.

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"The worst thing about 'I'm Still Here' is the fact that it exists," wrote Dana Stevens, for Slate. But Entertainment Weekly critic Owen Gleiberman saw artistic merit in the film, writing that "Affleck uses Phoenix's descent to forge a riveting — and, in its way, cautionary — case study of a celebrity self-destructively addicted to his own psychodrama."